The present invention relates to a device used for the on-site fitting of a connector on a coaxial cable. The application of the invention lies, more particularly, in the field of digital telecommunications.
Links within a telecommunications network are made using cables and directional radio. Directional radio involves point-to-point links using microwaves in the range 1 GHz-50 GHz as the transmission medium. A radio link makes it possible to establish two-way communication between two terminal stations, it being possible for the communication to be routed via intermediate stations separated from one another by about 50 kilometres. Each station is then connected to a telecommunications landline network.
The equipment of these stations essentially consists of an antenna and a transmitter/receiver. The antenna is usually composed of a horn-shaped aperture which radiates a wave carried by a wave guide, and one or more deflectors of parabolic general shape. The radiating aperture is always located at the focus of the parabola. The waveguide is connected by its other end to a transmitter/receiver located in a room close to the antenna.
However, the waveguide is a very expensive transmission medium. Therefore, in order to limit the length of the waveguide, the transmitter/receiver has for some years been installed directly on the antenna. The transmitter/receiver is then connected to the antenna via a short waveguide and to the telecommunications landline network via a coaxial cable which is less expensive than the waveguide.
The coaxial cable is a high-frequency medium consisting of an inner copper conductor surrounded by a concentric screen, made of copper or aluminium and in principle at the potential of the earth. They are separated by a polyethylene dielectric. The cable is furthermore covered with an insulating sheath.
In order to make it easier to install the coaxial cable on the pylon which supports the antenna, and in order to adjust its length optimally, the connector joining the cable to the transmitter/receiver is fitted once the cable is in place. The connector essentially comprises a core and a ferrule. The core is a hollow metal rod into which the central conductor of the coaxial cable is inserted and soldered. The ferrule is a metal ring which will be placed around the screen of the cable.
The operations which need to be carried out on the coaxial cable when fitting a connector to the cable are essentially operations of cutting and stripping the insulating sheath of the cable. This preparation of the cable is followed by a step of positioning and welding the elements of the conductor on the coaxial cable.
FIGS. 1A and 1B illustrate the positioning of two types of connectors on coaxial cables having different diameters. In both figures, a connector consisting of a core 1 and a ferrule 2 is fitted on a coaxial cable 3. Orifices 5 and 6 are provided respectively in the core 1 and in the ferrule 2 in order to solder the core 1 on the central conductor 4 of the coaxial cable 3, and the ferrule 1 on the screen of this coaxial cable 3. The connectors which are represented are of the N type in FIG. 1A and of the TNC type in FIG. 1B. The dimensions of the elements of the connectors differ according to the type of connector. The positioning of the core 1 on the coaxial cable 3 is represented by a value d in FIG. 1A and by a value d' in FIG. 1B. These values represent the distance between a shoulder situated close to the tip of the core and the end of the polyethylene dielectric. The values d and d' are respectively 15 millimeters and 6 millimeters.
The quality of the fitting of the connector on the coaxial cable is of essential importance in the field of digital telecommunications. This is because the transmission of digital data will not tolerate possible bad contacts in the connector. Bad contacts of this type often give rise to synchronization losses or breaks in connection.
However, it may sometimes be very difficult to fit the connectors. This is because the operation is generally carried out on site, at windy places and in all weathers. In the case of maintenance, these unfavourable working conditions are further aggravated by the fact that it is common practice to work at night, when the network activity is less.
It will then be understood that all these conditions can lead to connection faults.